The present invention relates generally to an apparatus and method for performing a thermotherapy patient treatment protocol. More particularly, the invention relates to a novel apparatus and method for heating the prostate gland for therapeutic purposes.
Thermotherapy treatment is a relatively new method of treating diseased and/or undesirably enlarged human prostate tissues. Hyperthermia treatment is well known in the art, involving the maintaining of a temperature between about 41.5xc2x0 through 45xc2x0 C. Thermotherapy, on the other hand, usually requires energy application to achieve a temperature above 45xc2x0 C. for the purposes of coagulating the target tissue. Tissue coagulation beneficially changes the density of the tissue. As the tissue shrinks, forms scars and is reabsorbed, the impingement of the enlarged tissues, such as an abnormal prostate, is substantially lessened.
The higher temperatures required by thermotherapy require delivery of larger amounts of energy to the target prostate tissues. At the same time, it is important to shield nontarget tissues from the high thermotherapy temperatures used in the treatment. Providing safe and effective thermotherapy, therefore, requires devices which have further capabilities compared to those which are suitable for hyperthermia.
Though devices and methods for treating benign prostatic hyperplasia have evolved dramatically in recent years, significant improvements have not occurred and such progress is badly needed. As recently as 1983, medical textbooks recommended surgery for removing impinging prostatic tissues and four different surgical techniques were utilized. Suprapubic prostatectomy was a recommended method of removing the prostate tissue through an abdominal wound. Significant blood loss and the concomitant hazards of any major surgical procedure were possible with this approach.
Perineal prostatectomy was an alternatively recommended surgical procedure which involved gland removal through an incision in the perineum. Infection, incontinence, impotence or rectal injury were more likely with this method than with alternative surgical procedures.
Transurethral resection of the prostate gland has been another recommended method of treating benign prostatic hyperplasia. This method required inserting a rigid tube into the urethra. A loop of wire connected with electrical current was rotated in the tube to remove shavings of the prostate at the bladder orifice. In this way, no incision was needed. However, strictures were more frequent and repeat operations were sometimes necessary.
The other recommended surgical technique for treatment of benign prostatic hyperplasia was retropubic prostatectomy. This required a lower abdominal incision through which the prostate gland was removed. Blood loss was more easily controlled with this method, but inflammation of the pubic bone was more likely.
With the above surgical techniques, the medical textbooks noted the vascularity of the hyperplastic prostate gland and the corresponding dangers of substantial blood loss and shock. Careful medical attention was necessary following these medical procedures.
The problems previously described led medical researchers to develop alternative methods for treating benign prostatic hyperplasia. Researchers began to incorporate heat sources in Foley catheters after discovering that enlarged mammalian tissues responded favorably to increased temperatures. Examples of devices directed to treatment of prostate tissue include U.S. Pat. No. 4,662,383 (Harada), U.S. Pat. No. 4,967,765 (Turner), U.S. Pat. No. 4,662,383 (Sogawa) and German Patent No. DE 2407559 C3 (Dreyer). Though these references disclosed structures which embodied improvements over the surgical techniques, significant problems still remained unsolved.
Recent research has indicated that enlarged prostate glands are most effectively treated with higher temperatures than previously thought. Complete utilization of this discovery has been tempered by difficulties in shielding rectal wall tissues and other nontarget tissues. While shielding has been addressed in some hyperthermia prior art devices, the higher energy field intensities associated with thermotherapy necessitate structures having further capabilities beyond those suitable for hyperthermia. For example, the symmetrical microwave-based devices disclosed in the above-referenced patents have generally produced relatively uniform cylindrical energy fields. Even at the lower energy field intensities encountered in hyperthermia treatment, unacceptably high rectal wall temperatures have limited treatment periods and effectiveness. Further, while shielding using radioreflective fluid has been disclosed in the prior art (see for example European patent application No. 89,403,199) the location of such radioreflective fluid appears to increase energy field intensity at the bladder and rectal wall. This is contrary to one of the objects of the present invention.
In addition, efficient and selective cooling of the devices is rarely provided. This increases patient discomfort and increases the likelihood of healthy tissue damage. These problems have necessitated complex and expensive temperature monitoring systems along the urethral wall.
Finally, the symmetrical designs of the above-referenced devices do not allow matching of the energy field to the shape of the abnormally enlarged prostate gland. Ideally, the energy field reaching the tissues should be asymmetric and generally should expose the upper and lateral (side) impinging lobes of the prostate gland to the highest energy. In addition, the field is ideally substantially elliptical such that the energy reaching the sphincters is minimized.
It is therefore an object of the invention to provide an improved apparatus and method suitable for ultrasound treatment of tissue.
It is a further object of the invention to provide an improved apparatus and method for thermotherapy treatment which provides a smaller probe with higher ultrasound energy output on target tissues.
It is yet a further object of the invention to provide a novel method and apparatus having high ultrasound energy output on target tissues while producing substantially no energy output directed to nontarget tissues.
It is yet another object of the invention to provide an improved applicator designed to be inserted into an orifice of a male patient, wherein the applicator includes a small diameter ultrasound probe.
It is a still further object of the invention to provide a novel means for dynamic monitoring of the treatment temperature distribution and to use such information to aid in the control of the deposited power level and its distribution.
It is another object of the invention to provide an improved ultrasonic applicator which can be inserted into the urethra and can be positioned with respect to the prostate and maintained in position during treatment.
It is a further object of the invention to provide an improved method and apparatus using ultrasound energy for the treatment of prostate disease and, more particularly to provide an ultrasound applicator consisting of multiple transducers which can be inserted into the urethra or rectum and direct the energy in such a manner as to selectively treat the prostate gland.
It is yet another object of the invention to provide a novel method and apparatus utilizing ultrasound energy to achieve therapeutic temperatures in the prostate with better control of power deposition spatially within the prostate gland than is possible with prior art devices.
It is an additional object of the invention to provide an array of ultrasound transducers producing an energy field having a gap or xe2x80x9cdead zonexe2x80x9d whereby tissues (such as the rectum, the distal sphinchter and the verumontanum) are protected from energy transmission.
It is a further object of the invention to provide improved control of both the ultrasonic power level and the distribution of the power deposited in the prostate in a dynamic fashion which compensates for physiological changes (temperature, blood flow effects) that can occur during therapy and accommodates operator-desired alterations in the therapeutic energy distribution within the prostate.
It is another object of the invention to provide an improved thermotherapy device which includes a collimated irradiation of a target zone generally and selective cooling of nontarget tissues.
It is still an additional object of the invention to provide an improved thermotherapy device which reduces tissue damage and discomfort by providing more effective cooling to nontarget tissues.
It is an additional object of the invention to provide an improved thermotherapy apparatus having one or more extended, and nondistensible but expandable balloons.
It is an additional object of the invention to provide an improved thermotherapy device which includes ultrasound transducers or other energy sources capable of producing a substantially asymmetric energy output field, thus minimizing energy reaching the rectal wall in benign prostatic hyperplasia thermotherapy treatment.
It is still a further object of the invention to provide an improved thermotherapy apparatus which produces an energy field shaped in accordance with the enlarged mammalian gland to be treated.
Other advantages and features of the invention, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, wherein like elements have like numerals throughout the drawings.